geniuspaste: Ask confirmation before pasting

[b4n]

The pasted data might contain sensitive information and the pastebin service might be public and might not allow deleting a paste (at least not in a way the plugin supports). Thus, ask confirmation by default in case the user accidentally triggered the action.

@xiota does this make you a tad more comfortable? The UI isn't stellar, but it gets the job done and fearless users can disable it.